Son of James Ferguson and Anne Murray. Student at Royal Military Academy in Woolwich (1759-1761). Officer in the Royal North British Dragoons (the Greys) (1759-1768). In active service in Germany during the Seven Years War 1761-1762. In the West Indies with the 70th Foot (1769-1772). He eventually rose to the rank of Lt-Col and Major. In the mid 1770s he invented the Ferguson Rifle, the first breech-loading rifle in the British Army.

Ferguson was in active service in North Ameria from 1777 until his death in the battle of King's Mountain on October 7, 1780. He was wounded at the Battle of Brandywine on September 11, 1777, where he reputedly had George Washington in his gun sight. He didn't shoot him for the gentlemanly reason that he didn't want to shoot a man in the back of the head.1